Asymmetrical V-Shape Rotor Configuration of an Interior Permanent Magnet Machine for Improving Torque Characteristics

In comparison to surface-mounted permanent magnet machines, IPM machines offer several advantages such as higher power density and wider speed range, since the PM is inserted into the rotor core. Such machines have been generally selected as drive motors widely applied in electrical vehicle, CNC machine tool and other variable speed applications. Nevertheless, due to this structural characteristic, IPM machines produce extremely higher cogging torque and more rectangularly distributed flux density in air gap, compared to SPM machines. In general, IPM machines are subjected to higher torque ripple due to cogging torque and harmonic torque, which causes the undesirable vibration and noise. The smooth electromagnetic torque is required for most applications. Thus, one of the most significant tasks for IPM machine design is to make torque ripple as small as possible. This study presents an asymmetry V-shape rotor configuration of IPM machines for improving torque characteristics. IPM machines with the asymmetry V-shape rotor configuration are better in torque characteristics.